Process for the preparation of alk(en)ylphosphoric ester salts

ABSTRACT

The invention relates to a process for the preparation of alk(en)ylphosphoric ester salts which comprises reacting the alk(en)ylphosphoric esters in the form of their melts with a base. Advantageously, the alk(en)ylphosphoric esters do not need to be dissolved in a solvent prior to neutralization.

[0001] The invention relates to a novel process for the preparation ofalk(en)ylphosphoric ester salts.

[0002] Alk(en)ylphosphoric esters have excellent properties asdetergents, and also a high emulsifying power and good ecotoxicologicalcompatibility.

[0003] Of increasing importance is the use of solid, solvent-freephosphoric esters, in particular salts thereof, which, due to theirneutral pH values, are very well tolerated by the skin and areadvantageous as emulsifiers in cosmetic and pharmaceutical formulations.

[0004] The alkyl- and alkenylphosphoric esters are prepared in a knownmanner by reacting tetraphosphorus decaoxide and fatty alcohols to formmono- and diesters with small fractions of triesters. The phosphoricesters are dissolved in solvents for neutralization, and then reactedwith bases, for example NaOH or KOH.

[0005] JP 62 198 690 describes the neutralization of phosphoric estersin a hydroxyl-containing, water-soluble reaction medium, for examplepropylene glycol.

[0006] For economical, ecological and performance reasons it would bedesirable to find a solvent-free method for the preparation ofalk(en)ylphosphoric ester salts.

[0007] Surprisingly, it has now been found that alk(en)ylphosphoricesters in the form of their melts can be neutralized with a concentratedaqueous or solid base to give alk(en)ylphosphoric ester salts.

[0008] Since the alk(en)ylphosphoric esters are not dissolved in asolvent, subsequent stripping off of same is unnecessary. Moreover, theresidual water content in the alk(en)ylphosphoric ester salt can beminimized such that it is bonded as water of crystallization and doesnot have to be stripped off.

[0009] The invention provides a process for the preparation ofalk(en)ylphosphoric ester salts of the formula (I) and/or of the formula(II)

[0010] in which

[0011] R¹ and R² are identical or different and, independently of oneanother, are a linear or branched alkyl or alkenyl radical having 6 to30 carbon atoms and X^(n+) is a cation with the valency n, where n is aninteger, which comprises reacting alk(en)ylphosphoric esters of theformula (III) and/or of the formula (IV)

[0012] in the form of their melts with a base from which the cationX^(n+) arises.

[0013] It may be expressly noted that the term base also includesmixtures of chemically different bases. In this case, thealk(en)ylphosphoric ester salts of the formulae (I) and (II) regularlycontain different cations X^(n+), which arise during the neutralizationfrom the various bases.

[0014] The radicals R¹ and R² are preferably alkyl or alkenyl radicalshaving 8 to 22 carbon atoms.

[0015] The alk(en)ylphosphoric esters of the general formulae (III) and(IV) are generally prepared by condensation of phosphorus pentoxide ororthophosphoric acid with fatty alcohols.

[0016] Preferred fatty alcohols are caproic alcohol, caprylic alcohol,2-ethylhexyl alcohol, capric alcohol, lauryl alcohol, isotridecylalcohol, myristyl alcohol, cetyl alcohol, palmoleyl alcohol, stearylalcohol, isostearyl alcohol, oleyl alcohol, elaidyl alcohol,petroselinyl alcohol, linolyl alcohol, linolenyl alcohol, elaeostearylalcohol, arachyl alcohol, gadoleyl alcohol, behenyl alcohol, erucylalcohol, brassidyl alcohol and mixtures thereof.

[0017] The preparation of the alk(en)ylphosphoric esters often producesmixtures of mono-, di- and triphosphoric esters, the pH of which isusually in the range 2 to 5.

[0018] Of preference for the reaction are mixtures with a monophosphoricester fraction greater than 60% by weight, preferably greater than 80%by weight. Fractions of triphosphoric esters do not interfere in thereaction.

[0019] The alk(en)ylphosphoric esters are preferably melted in amixing-kneading reactor.

[0020] The bases may be organic or inorganic bases which are suitablefor neutralizing the OH groups of the alk(en)ylphosphoric esters.

[0021] The base may be used as an aqueous solution, preferably as aconcentrated aqueous solution, suspension or in the form of a powder.The concentration of the aqueous solutions/suspensions is preferablygreater than or equal to 25% by weight, particularly preferably 50% byweight, especially preferably 75% by weight.

[0022] In a preferred embodiment, the total amount of water whichoriginates from the base and/or the water of neutralization is such thatit is bonded as water of crystallization in the solid phosphoric estersalt.

[0023] In a preferred embodiment, the base is used as a saturatedaqueous solution. In the case of saturated aqueous solutions, asufficiently good miscibility of the reactants with the simultaneousminimal introduction of water into the reaction mixture is ensured.

[0024] If the base is used in the form of a powder, this has theadvantage that no water is introduced via the base, and the water formedduring the crystallization is bonded as water of crystallization thesolid phosphoric ester salt. Subsequent removal of residual water fromthe product can be dispensed with.

[0025] Preferred bases are metal hydroxides, metal oxides, ammonia,primary amines, secondary amines, tertiary amines, alkanolamines and/oramino acids. Preferred metal hydroxides are alkali metal hydroxides,preferably NaOH and KOH, alkaline earth metal hydroxides, preferablyCa(OH)₂, and alkaline earth metal hydroxides, preferably AI(OH)₃.

[0026] Preferred amines are primary amines with long-chain alkyl or arylradicals having 6 to 30 carbon atoms, particularly preferably 16 to 22carbon atoms.

[0027] Preferred alkanolamines are monoethanolamine, diethanolamine andtriethanolamine.

[0028] Particularly preferred bases are alkali metal hydroxides,particularly preferably NaOH and KOH, very particularly preferably KOH.

[0029] Accordingly, the cations X^(n+) in the formulae (I) and (II) arepreferably metal ions, NH₄ ⁺ and ammonium ions derived from amines,alkanolamines and amino acids. Preferably, n has the value 1, 2 or 3,particularly preferably 1 or 2, very particularly preferably 1.

[0030] The equivalent molar ratio of phosphoric ester(s) to base ispreferably in the range 1:0.1 to 1:10, particularly preferably 1:0.5 to1:2, especially preferably 1:0.9 to 1:1.1. Very particularly preferably,the ratio is 1:1.

[0031] The reaction of the alk(en)ylphosphoric ester with the basepreferably takes place at temperatures of from 50 to 300° C.,particularly preferably 100 to 180° C., over a period of from 0.1 to 10hours, particularly preferably 0.1 to 5 hours, especially preferably 0.1to 3 hours.

[0032] Advantageously, the reaction temperature is above the meltingpoint of the end product, since sufficiently miscibility of thereactants is then ensured.

[0033] The alk(en)ylphosphoric esters are preferably initiallyintroduced as melts and then reacted with the base.

[0034] The reaction is preferably carried out with mixing/kneading,preferably in a mixing-kneading reactor.

[0035] Surprisingly, it has been found that the quality andprocessability of the products increases if the reaction mixture ismixed/kneaded following the reaction at 50 to 300° C. for a further 0.1to 6 hours at room temperature.

[0036] The mixing/kneading preferably takes place in a mixing-kneadingreactor.

[0037] The products which are produced can be readily drawn off as ablock product or flaked to give a flaked product or be drawn off in theform of pellets.

[0038] The alk(en)ylphosphoric ester salts prepared according to theinvention are suitable for use in cosmetic and pharmaceuticalformulations, in particular for the preparation of oil-in-wateremulsions, but also of water-in-oil emulsions. They are preferablysuitable for the preparation of alcohol-free emulsions.

[0039] The alk(en)ylphosphoric ester salts are usually used in amountsof from 0.1 to 10% by weight, preferably 0.3 to 4% by weight, based onfinished formulations.

[0040] The emulsions can be used as skincare compositions, such as, forexample day creams, night creams, care creams, nutrient cream, bodylotions, ointments and the like. Further auxiliaries and additives whichmay be present are, inter alia, oily bodies, coemulsifiers, superfattingagents, fats, waxes, stabilizers, biogenic active ingredients, glycerol,preservatives, dyes and/or fragrances.

[0041] The examples below serve to illustrate the invention in moredetail without, however, limiting it thereto. All percentages given arepercentages by weight.

EXAMPLE 1 Preparation of the Potassium Salt of the Monocetyl PhosphoricEster

[0042] 1) Initial charge of 670 g of ®Hostaphat CC 100 (monocetylphosphate, Clariant) in the mixing-kneading reactor (List) as melt at atemperature of 120° C.

[0043] 2) Dissolution of 111.4 g of KOH pellets in 40 g of water at 80to 90° C.

[0044] 3) Slow addition of the KOH solution at about 80° C. into theoperating kneader

[0045] 4) Vigorous kneading at 150° C. for 15 minutes

[0046] 5) Vigorous kneading at room temperature for a further 3 hours inan open mixing-kneading reactor, during which granulation takes place asa result of cooling

[0047] 6) Formulation by grinding.

[0048] The product was a white to slightly yellowish powder with amelting point of from 120 to 130° C.

EXAMPLE 2

[0049] Preparation of the Potassium Salt of the Monocetyl PhosphoricEster

[0050] 1) Initial charge of 670 g of ®Hostaphat CC 100 (monocetylphosphate, Clariant) in the mixing-kneading reactor (List) as melt at atemperature of from 160 to 180° C.

[0051] 2) slow addition of 111.4 g of KOH powder

[0052] 3) vigorous kneading at 160 to 180° C. for 3 hours

[0053] 4) vigorous kneading at room temperature for a further 3 hours inan open mixing-kneading reactor, during which granulation takes place asa result of cooling

[0054] 5) formulation by grinding.

[0055] The product was a white to slightly yellowish powder with amelting point of from 120 to 130° C.

1. A process for the preparation of alk(en)ylphosphoric ester salts ofthe formula (I) and/or of the formula (II)

in which R¹ and R² are identical or different and, independently of oneanother, are a linear or branched alkyl or alkenyl radical having 6 to30 carbon atoms and X^(n+) is a cation with the valency n, where n is aninteger, which comprises reacting alk(en)ylphosphoric esters of theformula (III) and/or of the formula (IV)

in the form of their melts with a base from which the cation X_(n+)arises.
 2. The process as claimed in claim 1, wherein the radicals R¹and R² are alkyl or alkenyl radicals having 8 to 22 carbon atoms.
 3. Theprocess as claimed in claim 1, wherein the alk(en)ylphosphoric estersare a mixture comprising alk(en)ylphosphoric esters of the formulae(III) and (IV), where the proportion of alk(en)ylphoshoric esters of theformula (III), based on the mixture, is greater than 60% by weight. 4.The process as claimed in claim 1, wherein the base is a concentratedaqueous solution or a powder.
 5. The process as claimed in claim 4,wherein the base is a saturated aqueous solution.
 6. The process asclaimed in claim 1, wherein the base is selected from the groupconsisting of metal hydroxides, metal oxides, ammonia, primary amines,secondary amines, tertiary amines, alkanolamines, amino acids, andmixtures thereof.
 7. The process as claimed in claim 6, wherein the baseis an alkali metal hydroxide and/or an alkaline earth metal hydroxide.8. The process as claimed in claim 7, wherein the base is selected fromthe group consisting of NaOH, KOH, Ca(OH)₂, and mixtures thereof.
 9. Theprocess as claimed in claim 1, wherein an equivalent molar ratio ofalk(en)ylphosphoric esters to the base is in the range 1:0.1 to 1:10.10. The process as claimed in claim 1, wherein the reaction takes placein a reaction mixture at temperatures of from 50 to 300° C. over aperiod of from 0.1 to 10 hours.
 11. The process as claimed in claim 10,further comprising mixing/kneading the reaction mixture following thereaction at 50 to 300° C. for a further 0.1 to 6 hours at roomtemperature.
 12. The process as claimed in claim 1, wherein thealk(en)ylphosphoric esters are initially introduced as melts and arethen reacted with the base.
 13. The process as claimed in claim 1,wherein the reaction is carried out with mixing/kneading. [, preferablyin a mixing-kneading reactor.]
 14. The process as claimed in claim 1,wherein the alk(en)ylphosphoric esters are a mixture comprisingalk(en)ylphosphoric esters of the formulae (III) and (IV), where theproportion of alk(en)ylphoshoric esters of the formula (III), based onthe mixture, is greater 80% by weight.
 15. The process of claim 7wherein the base is KOH.
 16. The process of claim 9 wherein theequivalent molar ratio is 1:0.5 to 1:2.
 17. The process of claim 9wherein the equivalent molar ratio is 1:0.9 to 1:1.1.
 18. The process asclaimed in claim 1, wherein the reaction takes place in a reactionmixture at temperatures of from 100 to 180° C., over a period of from0.1 to 5 hours.
 19. The process as claimed in claim 1, wherein thereaction is carried out in a mixing-kneading reactor.